Fluid heater



Dec. 19, 1939. N. c. PRICE FLUID HEATER vFiled Jap. 12,v 1937 mnmyy@munmwn :Aulwll l l l l l l l l l l l I I l l l l l I I l l l l l llPatented Dec. 19., 1939 UNITED sTATl-:s PATENT ol-Flcs Nathan C. Price,Berkeley, Calif., assignor to vSirius Corporation, a corporation ofCantornia"A IAppumiml January 12, 1931, serial 10.120,188 v is claims.(ci. 12a-zsm The invention relates to fluid heaters and particularly tovapor generators such as steam boilers employing liquid or gaseous fuelas the heating medium.

An object of the invention is to provide a vapor generator which isparticularly applicable for uses where lightness and compactness is ofimportance, such as in moving vehicles.

Other objects which are to be satisfied comprise, first,l attainment ofeffective thermal counteriiow between gases of combustion and ytheworking fluid for high efficiency, second, ability to pre-heat the airfed to the combustion chamber in a manner which will reduce the amountof boiler insulation required and which will entail v a minimum ofstructural material, third, ease of inspection of all heated-surfacesand simplicity of construction, fourth, properl support of the heatedsurfaces to allow free thermal expansion and contraction eliminatingharmful temperature stresses, fifth, ability to withstand explosions inthe combustion chamber without structural damage, sixth, proportioningof much 'greater heat transfer area to the gases of combustion than tothe working fluid thereby reducing the weight per vapor output ratio ofthe boiler and lessening heat storage, seventh, convergence ofcombustion gas flow passages in the direction of ow to establishsubstantially constant heat transfer from the inlet to the -outlet c-fthe boiler, and eighth, integration ofthe air supply system with theboiler# The invention possesses other advantageous features which areevident in the illustrated form accompanying the followingspecifications.

Figure 1 is a section through the principal axis of one form of theinvention showing a cylindrical vapor generator integrally combined withits air preheater, fuel injector, fuel igniter, and air supply pump in,ya manner providing advantageous relationship between the variouselements. /f/

Figure 2 is a quarter end view of Figure 1, re

vealing a fragment of section normal to the principal axis as designatedbythe letter A in Figclose-wound superheater helical `coil Il, aconvergent combustion gas conducting space I5, a convergent cylindricalcombustion shroud Il, and a combustion chamber 3|.

Feed liquid is supplied to the inlet 4- of the economizer co'il I1,which comprises a tube 23 with numerous spaced circular fins thermallybonded thereto.

At a region 34 the coll I1 is serially joined to the coil I4 andconducts evaporating working iiuid thereto. Progressivesuperheating ofth working fluid is accomplished in the coil I4 and in a serialclose-wound coil I3, which is both conical and spiral. The conditionedworking fluid is discharged from an outlet duct 5 to the con-- sumer. f

chamber i and vignition regulation for this boiler is fullyv shown in myPatent No. 2,064,494 entitled "Control system."

The heating system illustratedI in Figure 1 includes an electric motor Ifor rotating a centrifugal blower impeller 2. Supply air enters an inlet5 and is discharged into a diffuser 3` for partial conversion ofvelocity head to pressure head.

The diffuser 3' is formed as a heat exchanging structure, which isintegral with a series of flues I8. It also comprises a -boiler endplate 22 to which the'envelcpe I0 is mechanically joined.

The iiues I8 are shaped and angularly posi-I tioned to form a tangentialand divergent arrangement of diffuser vanes for high efficiency.

Furthermore a structurally sound boiler end plate is produced since theiiues 'I8 act as stiftening webs. The blower imponer-2 is placed in anideal position from the standpoints of directness of discharge andcompactness.

The partially heated airleaving the diffuser 3'is directed along the airpreheating duct l to extract more heat` from the envelope Ill, andfinally passes at a relatively high temperature through s'orne ns Sintothe combustion chamber 3I.

The fins 9 are formed-tangent to a' ircle about the boiler principalaxis B in order to impartv a twist to the incoming air as shown in Fig.3. l

The resultant rotating mass of air strikes a fuel spray envelope 21issuing frcmla mechanical atomizing burner nozzle 30 of centrifugaltype. Integralwith the burner nozzle 30 are a fuel supply line 23, andan ignition plug 23 forllghting thc fire. y Preferably the'rotation afthe fuel spray en velope is made opposite to that of the incoming' air,to produce thorough mixing. However, the

heater duct 1, the heated inner portions of theY boiler, such as thecoil I4, the coil I1, and the moment of momentum 'ofthe air is greater.than that of all the fuel droplets. A net rotation of the mixtureresults. y,Large droplets of fuel which burn slowly tendto become forcedcentrifugally against the hot shroud Il, where they rapidly vaporize anddo not reach the boiler tubing.

The gases of combustion issue from the slightly conical chamber 3| andare deflected by a sea1` ing disc I2 and the coil I3. Reversed directionflow along the space I5 results;

The space I5, bounded by the coil I4 and the shroud II, is madeconvergent in direction of flow in order to maintain approximately thesame rate of heat transfer throughout the entire length of the innerside of the coil I4. L

When the gases of combustion reach the region 34, they are againreversed in direction of flow by a flange 35 of the shroud`II, and passbetweenthe ns 24, the coil I4, and the envelope I to be finallydischarged from the ues I8. A naturally high heat transfer existsbetween the liquid inthe coil I1 and the inside of the tube 23 due tothe -thermal conductivity characteristi'cs of liquids, while the gasesof combustion on the otherhand have intrinsically poor heat conductivecapabilities.

Therefore, there is a considerable economy realized in material andspace by utilizing means for obtaining of a much greater heating surfaceto the gases of combustion than to the economizer liquid. This isaprimary function of the ns 24.

Furthermore, the fins serveas spacing means between adjacent loops ofthe coil I1, and between the coil I4 and the envelope I0.

Due to the free space constituting the air preenvelope I0, are able toexpand radially as temperature changes occur.

, The combustion chamber shroud II is capable of expanding in alldirections due to the space I5 surrounding it.

The various loops of the coil I3 are also `free to expand due to theconical shape of the spiral.

For supporting the inner portions of the boiler axially, some spacingblocks 32 mechanically iix the periphery of the coil I3, to the boilerend plate 22. Some studs I 9 threaded into the casing 8 serve with theirnuts 20,and so'me coil springs 2| to hold a sealing slip-joint 33between the casing 8 and the plate 22, at a minimum gap.

Accordingly the casing 8 producesaxial pressure through the tangentialfins 9 upon the flange 35 of the shroud II. This flange bears upon thecoil I1 and the coil I4 which in turn compress the periphery of thespiral coil I3.

The flange 35 is Vsealed to the envelope I0 by a slip-joint 26.

.Therefore, as the temperature of.-the inner portionof the boilerincreases relative to that of the casing 8, differential expansion alongthe principal axis B is permitted by the resultant compression of thesprings 2|.

Likewise in event of .delayed ignition in the combustion chamber and asubsequent explosion, the springs 2l act as energy absorbing members toprevent rupture of the boiler casing. Also it is provided that underthiscondition the casing 8 may be moved so far axially from the plate 22,that direct pressure relief passages for gases are created through theslip-joint 26 and the slipjoint 33.

Above the broken Aline is revealed a section of Figure 1 taken at theletter A in Figure 1. Below the broken line an .external end view ispresented.

In Figures 1, 2, and 3 I have illustrated one form of uid heaterembodying my invention, but as set forth in the claims, it may beembodied in a plurality of forms.

I claim: 1. A boiler comprising a cylindrical envelope surrounding insubstantially coaxial relationship and in the following sequence in thedirection of the axis, an economizer tube helical coil having finsextending from the surface thereof, a smooth superheater tube helicalcoil, and a combustion chamber, said last named coil and said envelopedefining a combustion gas flow path between said fins and parallel'tosaid axis, means for supplying feed liquid to said economizer coil, andsaid super heater coil being connected to said economizer coil forheating vapor of said liquid.

2. In apparatus of the character described in claim 1, said finsabutting said superheater tube coil and thereby aligning saidsuperheater coil with respect to said economizer coil.

3. In apparatus of the characterdescribed in claim 1,. a. cylindricalrefractory shroud surrounded by said superheater coil and bounding said`combustion chamber, an annular space lying between. said shroud and saidsuperheater coil for conducting gases of combustion from said chamber incounterflow to the boiler working fluid in said superheated coil, andsaid space converging in the direction of ow of said gases therebymaintaining the heat transfer to said superheater coil substantiallyconstant along th'e tubular length of said superheater coil.

4. In apparatus of the character described in claim l, said envelopebeing heat conductive, a cylindrical boiler .casing surrounding saidenvelope, an annular duct lying between said casing and said envelopefor preheating air for said combustion chamber, and means forforcingsaid 'air' to flow in said duct counter toand in heattransferring relationship to the gases of combustion passing betweensaid fins. l

5. In apparatus of the character described in claim l, said envelopebeingheat conductive, a cylindrical boiler casing surrounding saidenvelope, an annular duct lying between said casing and said envelopefor preheating air for said combustion chamber, a blower for forcingsaid air along said duct counter to and in heat transferringrelationship to the gases of combustion passing between said fins, andmeans for imparting a rotary motion about the boiler axis to said airthereby increasing the absorption of heat from said gases of combustion.

6. In. apparatus of the character described in claim l, said envelopebeing heat conductive, a cylindrical boiler casing surrounding saidenvelope, an annular duct lying between said casing and said envelopefor preheating air for said combustion chamber, a compressor' forforcing said air along said duct counter to and in heat bustion passingbetween said iins, and a tangential flow passage connecting said duct tosaid combustion chamber for producing an air swirl about the boiler axisin said chamber.

'7. In apparatus of the character described in claim 1, said envelopebeing heat conductive. an annular duct extending about said envelope forpreheating air for said combustion chamber, a cylindrical boiler casingsurrounding said duct,

a compressor for forcing said air along said duct in counterfiow to andin heat transferring-relationship to the gases of combustion passingbetween said lns, means for imparting a rotary motion `about the boileraxis to said air thereby increasing the heat transmission from saidgases to said lair, and a tangentialilow passage communicating betweensaid duct and said chamber coincident in direction tothe rotary motionin said duct. 1

8. A boiler tube comprising, a cylindrical boiler casing surrounding insubstantially coaxial relationship and in sequence in the directionofthe axis of said casing, an annular air preheating duct, a cylindricalheat lconductive envelope, a finned economizer tube helical coil,-a-smooth L y superheater tube helical coil having closely wound loops forheating vapor of said liquid, and a cylindrical combustion chamber,means for forcing feed liquid into said economizer coil, a flow passageextending from said chamber along said superheater `coil for heatcontribution thereto,V

and an extension of said passage along said economizer coil and saidenvelope for heat contribution thereto.

` 9. In apparatus of the character described in claim 8, a centrifugalblower, a diffuser ,for said blower constructed of spaced plates, saidplates having hollows, and means for conducting gases of combustion fromsaid extension through the hollows in said plates.

10. A boiler comprising, a cylindrical boiler casing surrounding insubstantially coaxial relationshipl and in sequence in the direction ofthe axis of "said casing, an annular air preheating duct, a cylindricalheat conductive envelope, a boiler tubehellcal coil, and a combustionchamber, a pump for forcing feed liquid into said coil, a centrifugalcombustion airimpeiler at one end of said duct, said impelle'r having anaxis of rotation coincident with the axis of said casing, a diffuser forsaid impeller constructed of spaced plates arranged tangentially aboutthe periphery of said impeller, said plates having hollows, a iiowpassage extending from said chamber along said coil for heatcontribution thereto, and said passage being connected to said hollows.

11. A forced circulation boiler comprising a long once-through boilertube having an inlet at one end thereof, an outlet at the other endtheref, and a change of state zone intermediate'of said ends, said tubebeing directly` exposed to`I flow of gases of combustion alongsubstantially the entire length thereof from said inlet endrto saidoutlet end, feed liquid alimentation means. at said inlet, working vapordisposal means atv said outlet, a cylindrical envelope encompassing saidtube. a combustion chamber for producing said gases, said chambercommunicating with the interior of said envelope, an air compressorconnected to said chamber, said tube having a relatively constantinternal diameter along its length from said inlet to said outlet, saidliquid having a relatively high thermal conductivity, said vapor havinga relatively low thermal conductivity, finlike projections on. thesurface of said tube,` and said projections being substantiallyproportionate to th`e thermal conductivity of `the iluid being conveyedwithin said tube opposite thereto at each increment of the tube length.

` 12. kA boiler` comprising a first helical boiler tube having heatconductive fins on the external 7surface thereof, a ow passage betweensaidv fins.'-

for forcing said fluid along said passage, anda second helical boilertube closely bounding said passage on one lateral side thereof.

13. A boiler comprising a boiler tube helical coil containing liquid andhaving a plurality Vof heat conductive i'lns extending from the externalsurface thereof, said fins being disposed trans-vl versely to the axisof Isaid tube, a cylindrical envelope abutting said ilns at one lateralside of the` edges of said fins, a boiler tube system containing vaporand abutting said iins at the'opposite'lateral side of the edges of saidfins, means for proa tube and abutting the edges of said ilns attheoutward side of said fins, a combustion chamber,

ducing -a relatively hot fluid, and a displacer for;` v

an annular duct lying between said casing and said envelope forpreheating combus n air for said chamber, a close-wound superhe ter tubehelix encompassed byfsaid economizer tube and abutting the edges of saidns at the inward side ofl said fins, anair compressor connected to saidduct, and said combustion chamber being connected to the space betweensaid iins.

15. A boiler comprising. a'cylindrical combustion chamber,` a helicalboilerA tube system surrounding said chamber, an annular air ductsurrounding said system, an imperforate cup-shaped casingsurroundingsaid duct and having a conoidal end projecting into saidchamber, an air compressor connected to one end of said duct,

a disc-shaped passage connecting the oppositel end of said duct to saidchamber, a plurality of tangential vanes in said passage, and a fuelinjection nozzle facing into said .chamber at the center of said end.NATHAN C. PRICE.

means for producing a relatively hot iluid, a pump v

